Antibiotic Susceptibility Profile and Tetracycline Resistance Genes Detection in Salmonella spp. Strains Isolated from Animals and Food

Abstract

Salmonella spp. is among the leading causes of foodborne infections in humans and a large number of animals. Salmonella spp. is a pathogen involved in the dissemination of antimicrobial resistance because it can accumulate antibiotic resistance genes (ARGs). In this study, the antibiotic resistance profile to 15 antibiotics, belonging to six different classes, of 60 strains of Salmonella spp. collected from pets, farm animals, wildlife, and food in Sicily (Italy) was investigated by the Kirby-Bauer method. Given that almost 33.3% of the Salmonella spp. strains were resistant to tetracycline, Real-Time PCR analysis was applied on all the 60 strains to detect the presence of eight selected tet resistance genes. Besides, the presence of the int1 gene, related to the horizontal gene transfer among bacteria, was also investigated in all the strains by Real-Time PCR analysis. Our data showed that 56% of the isolated strains harbored one or more tet resistance genes and that these strains were most frequently isolated from animals living in close contact with humans. Concerning int1, 17 strains (28.3%) harbored this genetic element and eight of these simultaneously contained tet genes. The results of this study highlight the importance of using a molecular approach to detect resistance genetic determinants, whose spread can increase the diffusion of multidrug-resistant strains. Besides, the study of zoonotic bacteria such as Salmonella spp. which significantly contribute to ARGs dissemination should always follow a One Health approach that considers the health of humans, animals, and the environment to be closely related.

Molecular Detection of Integrons, Colistin and β-lactamase Resistant Genes in Salmonella enterica Serovars Enteritidis and Typhimurium Isolated from Chickens and Rats Inhabiting Poultry Farms

“…In the current study, 21 (33.3%) of the isolates were multidrug-resistant. Our results are consistent with the findings of the previous studies conducted in Italy, Ghana and elsewhere in South Africa which reported multidrug resistance of 15%, 81.8% and 66.7% by Salmonella isolates, respectively [39][40][41].…”

Preliminary Results on the Prevalence of Salmonella spp. in Marine Animals Stranded in Sicilian Coasts: Antibiotic Susceptibility Profile and ARGs Detection in the Isolated Strains

“…However, despite the low incidence of phenotypic resistance, molecular analysis highlighted that these three strains all harbored at least one resistance gene for each of the four widely used classes of antibiotics: β-lactamases ( bla TEM and bla OXA ), tetracyclines ( tet (A), tet (D), and te t(E)), and sulfonamides ( sul I and sul II). The presence of these genes is reported in both phenotypically susceptible and resistant strains, but in order to contribute to antibiotic resistance the genes must be expressed [ 17 , 32 , 33 ]. Furthermore, ARGs are normally found linked to other resistance genes in integrons or on plasmids, and can therefore be transferred to other strains.…”

“…A short portion of 16S rDNA gene was used as positive control and nuclease-free water for molecular biology as negative control. Furthermore, one amplicon from each gene was sequenced to confirm the specificity of the PCR reaction by previously published protocols [ 17 ].…”

The Dynamics of the Antimicrobial Resistance Mobilome of Salmonella enterica and Related Enteric Bacteria

“…To date, 12 tetracycline resistance genes encoding RPPs have been reported, including tet M, O, Q, S, T, W, 32, 36, 44, B (P), otr (A), and tet ( Warburton et al, 2016 ). Many of the RPP determinants are located on mobile genetic elements (MGEs) within Salmonella , including transposons or plasmids, which may have facilitated their spread throughout the eubacteria via lateral gene transfer events ( Gargano et al, 2021 ). Another example of modification of antimicrobial targets is the wide dissemination of the plasmid-encoded chloramphenicol-florfenicol resistance (cfr) methyltransferase, which specifically methylates the adenine at position 2,503 in the 23S rRNA, thereby conferring resistance to a wide range of ribosome-targeted antimicrobials, including the phenicols, streptogramins, macrolides, and oxazolidinones (such as linezolid; Kaminska et al, 2010 ).…”